Conference 7.286::fddi

    It appears that you have bought more single-mode interfaces than you
    need.  The concentrator on the right has single-mode on the -FA port
    card and on the -DA A/B card.  You could run the single-mode fiber pair
    between the A port on the left concentrator and the B port on the right
    concentrator.  That would eliminate the need for the single-mode port
    card on the right concentrator.  Alternately, you could run the 
    single-mode fiber pair as shown (A to M) and eliminate the -DA card 
    altogether or buy the DAS ANSI version of the A/B card and save some $.
    
    	Also, when connecting a DAS (A/B) station to a SAS (M) station
    (this is considered a "dual-homing" configuration), the  DAS station
    will preferentially connect via the B port.  If someone were to connect
    the B port of the left concentrator to some other M port, the -CA card
    would break the single-mode connection.  If you really want to connect
    to the right concentrator via an M port, buy a -DA card for the
    concentrator on the left.  That will put the single-mode optics on the
    B port.
    
    	The bridges need only a single cable (fiber pair) to attach to the
    concentrator, however there must be MIC connectors on both ends.  I
    don't know what a BN24B cable has for connectors.  Lots of the cables
    we have in the lab have MIC on one end and ST on the other.

	I've made some changes. I'd like to go with a tree and connect the
    B-port to the M-port. As my diagram show, the DEFCN-CA on the right is
    for out-of-band management purposes only. That's why it's there. I had
    the correct cards, but didn't put them in the right place. The -DA card
    is now on the left and the -CA card is now on the right. As note 530.4
    and you both suggested, B-laser to M-port-laser.
    
    The BN24B is the FDDI-to-FDDI cable. Is this the MIC cable? I have also
    changed it by deleting DEFCN-NA on the right and attaching the
    DECbridge (DEFEB-TA) to one of the DEFCN-FA M-ports.
    
    This leaves me with 3 MM-ports on the left. On the right, I have 1
    Laser-M-port & 1 MM-port available.
    
    I'm also purchasing the DECMCC Director and the ELM AM for in-band
    management.
    
    Thanks for all your help.
    
    
    Concentrator				Concentrator
    Site A					Site B
    ------------				____________
    | DEFCN-AC |				| DEFCN-AC |
    ------------				------------
    | DEFCN-DA |<-Port B Laser <> M port Laser->| DEFCN-FA | -MModeport----
    ------------				------------              |
    | DEFCN-NA |				| DEFCN-CA | (MGMT only)  |
    ------------				------------              |
       	 | BN24B-10 (1 only)			     ----------------------
    	 |					     | 
    	 |					     | BN24B-10 (1 only)
    ------------				------------
    | DEFEB-TA |				| DEFEB-TA |
    ------------				------------
    
    
    
             MODEL NUMBER               
	QTY  AND DESCRIPTION            
       -------------------------------
        2  DEFCN-AC                   
           Configurable FDDI Con Box -  
    
        1  DEFCN-DA                  
           FDDI DECconcentrator 500     
           Remote Network Management    
           Module with FDDI A/B ports   
           ANSI Optics on Port A and    
           Laser Optics on Port B       
    
        1  DEFCN-CA                  
           FDDI DECconcentrator 500     
           Remote Network Management    
           Module with FDDI A/B ports   
           Laser Optics on Port A and   
           ANSI Optics on Port B        

        1  DEFCN-FA                  
           FDDI DECconcentrator 500     
           4-port module                
           2 ANSI compliant multi mode  
           fiber optic connections and  
           2 laser based single mode    

        1  DEFCN-NA                  
           FDDI DECconcentrator 500     
           4-port module                
           ANSI compliant optics        

        2  DEFEB-TA                  
           DECbridge 610 US Model       
           FDDI to Ethernet/802.3       
           Local area network bridge    
           One SAS FDDI port with       
           Multi-mode optics            
    
        2  BN24B-10 cables
    

    Can anyone comment on .2?

    Sorry for the delay, I was on vacation.  You are still recommending
    that the Site B concentrator have a laser port on its A/B card.  That
    seems like an unnecessary expense to me.  
    
    I found some BN24B cables in the lab which are MIC to MIC, so that
    looks OK.
    
    Regards,
    
    Steve

I agree with Steve's comments on the DEFCN-CA. A DEFCN-MB will provide the same
MNGMT functionality at a lower cost. However, the -CA offers a backup single-
mode connection if the -FA card fails.

Note that the DEFCN at site B is the root CON of this tree; if you want the
root at site A, swap the DEFCNs.